Discovery is ripping me off

I have medical savings of approximately R18 000 yet I'm told I have reached my annual optical Limit of R3850 therefor I must carry the shortfall of R630. I don't understand, what is the point of having medical savings if they won't pay out of it. You pick a high option so you can have a high annual med saving amount, I pay cash for all my over the counter meds, you try and ensure you go to doctors that are on the discovery network all in the name of medical savings account yet when you need them to pay they tell you stories. I use my medical savings prudently so that at times like these I will have funds, so what is the point of it all? So that year end you can transfer it, when this year you refuse to pay out claim. Last year I didn't go to an optometrist why doesn't the annual optical limit accumulate then so that when you need it, they can pay. I feel very ********** and used.